Helicocranchia Massy, 1907

Helicocranchia contains three recognized species. Voss, et al. (1992), however, suggest that as many as 14 species may exist.

Introduction

Species of Helicocranchia are small, oceanic squid (100 mm ML) characterized by having a very large funnel and small paddle-like fins that attach to a portion of the gladius that rises above the muscular mantle. They exhibit a gradual ontogenetic descent from near-surface waters as paralarvae to lower mesopelagic depths as near-adults.

Brief diagnosis:

A taoniin...

• with exceptionally large funnel relative to head and arms.
• with fins which project dorsally in advance of mantle apex.

Characteristics

1. Arms
   
2. Tentacles
1. Clubs with suckers only.
2. Tentacular stalks with two series of suckers and pads nearly to stalk base.
   
   
3. Funnel
1. Funnel valve absent.
2. Funnel organ: Dorsal pad with 3 slender papillae.
3. Funnel extremely large.
   

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   Figure. Side view of H. pfefferi, showing the large funnel and small arms. Photograph by M. Vecchione.

4. Mantle
1. Tubercles absent from funnel-mantle fusion.
   
   
5. Fins
1. Fins paddle shaped.
2. Fins insert on short rostrum-like structure of the conus of gladius which projects dorsally in advance of mantle apex (photographs below).* Toll (1882) suggests that the solid extension of the conus is not a true rostrum but was evolved independently for this peculiar support of the fins.
   
   

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   Figure. Views of the mantle tip and fins of H. pfefferi. Left - Dorsolateral view, Hawaiian waters. Photograph by R. Young. Right - Lateral view, N. W. Atlantic. Photograph by M. Vecchione.
   

6. Photophores
1. Single ocular photophore. (Difficult to detect in some species.)
2. Arm-tip photophores absent.
   

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   Figure. Left - Posterior and lateral views of the ocular photophore of H. papillata, 60 mm ML. Drawings from Voss, 1980, p. 383. Right - Ventral view of an eye of H. pfefferi showing the yellowish ocular photophore on the medial face of the eye, 35 mm ML. Photographed aboard the R/V G. O. SARS, Mar-Eco cruise, central North Atlantic by R. Young.

Comments

One of the most distinctive features of this genus is the extremely large funnel that extends well beyond the beaks. This feature, which recalls the large snout of a pig, gives the squid its common name. Characteristics are from Voss (1980).

Life History

The large funnel is present in the paralarva and makes generic identification of paralarvae easy. There is a near absence of an optic stalk making the eyes nearly sessile.

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Figure. Dorsal and ventral views of a paralarva of H. pfefferi, 3.4 mm ML, Hawaiian waters. Drawings by R. Young. The scale bar is 1 mm.

With increased age and depth of occurrence, Helicocranchia, becomes reddish in color probably as they start to mature sexually. Near sexual maturity many cranchiids apparently lose their tentacles. The insitu ROV images on the right below show that loss of tentacles is, indeed, normal.

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Figure. Left - Side view of H. pfefferi, central North Atlantic, female, 63 mm ML. Note the color and the absence of tentacles. Photographed aboard the MarEco cruise of the R/V G.O. SARS by R. Young. Right - two Insitu photographs of the same female Helicocranchia sp, anterolateral views, from an ROV photographed floating in front of oil pumping equipment in the Gulf of Guinea at a depth of 1015 m (SERPENT project). Arrow in upper photograph points to stub of tentacle.

Distribution

Vertical distribution

The distribution of Helicocranchia pfefferi from Hawaiian waters shows a clear pattern of ontogenetic descent with squid occurring in progressively deeper water as they get larger. Diel vertical migration does not seem to occur in this species. The dominance of nighttime captures for young stages is a result of the low sampling effort in shallow depths during the daytime and doesn't indicate the daytime absence of small squid at these depths.

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Figure. Vertical distribution chart of H. pfefferi, Hawaiian waters. Captures were made with both open and opening/closing trawls. Bars- fishing depth-range of opening/closing trawl. Circle- Modal fishing depth for either trawl. Blue-filled circles- Night captures. Yellow-filled circles- Day capture. Chart modified from Young (1978).

In the Atlantic Lu and Clarke (1975) show a similar vertical distribution pattern for Helicocranchia pfefferi. Most captures at less than 30 mm ML were made between 100 and 200 m. Around 30 mm ML an ontogenetic descent began although their largest specimen (49 mm ML) was taken between 300 and 400 m. Presumably the size/depth trend would continue for larger individuals.

Geographical distribution

Species occur throughout the world's tropical and subtropical oceans and, in the Atlantic Ocean, in north temperate waters (Voss, 1992).

Other Names for Helicocranchia Massy, 1907

• Vernacular Names: Piglet squid

References

Lu, C. C. and M. R. Clarke, 1975. Vertical Distribution of Cephalopods at 11° N 20° W in the North Atlantic. Journal of the Marine Biological Association of the United Kingdom, 55 (2): 369-389.

Toll, R.B. 1982. The comparative morphology of the gladius in the Order Teuthoidea (Mollusca: Cephalopoda) in relation to systematics and phylogeny. PhD. Dissertation, University of Miami, 390 pp.

Voss, N. A. 1980. A generic revision of the Cranchiidae (Cephalopoda; Oegopsida). Bull. Mar. Sci., 30: 365-412.

Voss N. A., S. J. Stephen and Zh. Dong 1992. Family Cranchiidae Prosch, 1849. Smithson. Contr. Zool., 513: 187-210.

Young, R. E. 1972. The systematics and areal distribution of pelagic cephalopods from the seas off Southern California. Smithson. Contr. Zool., 97: 1-159.

Young, R. E. (1978). Vertical distribution and photosensitive vesicles of pelagic cephalopods from Hawaiian waters. Fish. Bull., 76: 583-615.